Embodiments of the invention relate generally to systems that derive their power from fuel cells, and, more specifically, to an apparatus and method for improving the service life and efficiency of such systems.
Fuel cell technology has been incorporated in vehicles ranging from automobiles and buses to forklift trucks. While vehicles using fuel cell propulsion systems may produce low to near-zero emissions, incorporating fuel cell systems into such vehicles typically increases a cost of the vehicle (both in initial cost as well as in operating costs due to a relatively short service life of the fuel cell system) and reduces the range the vehicles may travel. Accordingly, acceptance of fuel cell technology vehicles has generally been limited in the marketplace.
Typically, fuel cell propulsion systems are sized to meet the peak transient requirements for system operation. In a fuel cell vehicle, peak transients generally occur over periods of steep acceleration, during which the system draws significantly more power from the fuel cell than during periods where the vehicle moves at constant speed. Sizing fuel cells to meet peak power requirements during periods of steep acceleration may result in vehicles which have fuel cells that are significantly larger than desired for the majority of driving situations.
Developing fuel cell vehicles with single fuel cells designed to meet the maximum power demand requirements, typically results in fuel cells that are expensive, heavy, and that have a short service life. Because the service lifetime of a fuel cell generally decreases as the total number of transients experienced by the fuel cell increases, having a single large cell may result in frequent replacement of one of the most expensive components in the vehicle. Because the cost of replacing a fuel cell can be a large percentage of the vehicle's total operating costs, decreasing the size of fuel cells and increasing the service life of the fuel cell are two factors in reducing the overall cost of operation of fuel cell vehicles.
It would therefore be desirable to have a fuel cell propulsion system that reduces the number of transients experienced by the fuel cell. It would also be desirable to have a propulsion system in which the size and cost of the fuel cell can be reduced from levels typical for current propulsion systems while offering performance comparable to systems having larger fuel cells.